1. Field of the Invention
This invention relates to separators, and, more particularly, to novel systems and methods for separating water and oil from petroleum production fluids.
2. Background Art
Gunbarrel separators are used for separation of water and oil, common “production fluids” in the petroleum industry. Typically, a gunbarrel separator amounts to a separating tank in which the lighter petroleum products rise through the heavier production water constituent. The system typically includes a flume amounting to a comparatively larger diameter tube that eventually feeds into a comparatively smaller diameter tube. These two tubes, the flume and the inlet tube, connected in series, result in transporting the entire inlet fluid mixture down through the center of the tank of a gunbarrel separator. Near the bottom of the tank, a distribution plate is attached like a flange around the inlet tube in order to enforce the distribution radially of the fluid mixture introduced into the tank. Thus, all of the mixture is introduced near the bottom of the tank.
Over time, the lighter species (e.g., crude oil or petroleous products), being lighter than the heavier species (e.g., water, brine) will rise through the heavier species. These eventually separate out to leave a lower quantity of the heavier species below an upper layer of the lighter species.
Also, one reason why the flume has a comparatively larger diameter than does the inlet line is that the production of an oil well may contain liquid (e.g., crude oil), including the liquid brine, as well as gases, including natural gas, air, and other trace compositions. Thus, by providing some space for the entrained gases to escape their mixture with liquid, and even to permit absorbed non-condensables to come out of solution, the flume acts as a liquid-gas separation chamber. Thus, the tank itself becomes primarily a liquid-liquid separator, separating lighter species from heavier species.
Gunbarrel separators, as well, as other types of separators, are typically tuned to a particular set of operating parameters. For example, oil, to be commercially useful, must have almost all the water removed. The percentage of water remaining affects the price of oil. However, gunbarrel separators are tuned (adjusted) to meet the dehydration specification for oil. The purity of the production water is often sacrificed to do so.
To be reinjected, put back down into injection wells or disposal wells, the brine needs to be stripped of crude oil products. The maxim “a clean well is a healthy well” refers to the fact that the porosity, efficacy, capacity, and so forth for an injection well depend on the constituents being placed down the well. Removal of solids, petroleum products, and the like assist in resisting fouling of the well, which would increase fluid dynamic drag on the injected flow as well as eventually sealing off the well and rendering it unsuitable for continued injection.
Scavenging unwanted constituents from effluents exiting separators is not relied upon in the oil and gas industry (petroleum production). Reducing unwanted fluid constituents down to percentages of less than a few percent is not done in that industry. Reducing below one percent or into parts per million of oil in water or water in oil is unheard of in the industry. Economics of equipment and throughputs would make such a concept irrational.
Thus, it would be an advance in the art to economically improve the operation of a gunbarrel separator or other separation system. Less water content in oil improves the quality thereof, and therefore the price. Likewise, it would be an improvement to provide a better mechanism for removing oil from the brine to be reinjected. Since injection wells have an allowed capacity, literally permitted by governmental permit, fouling a well destroys valuable capacity permitted for disposal in that well. Likewise, any oil stripped out of the water adds to the production “oil,” and is subject to the same parameters establishing its value if better dehydrated.